Double block for boats



FIG. 1 is a side view of the double block for boats;

FIG. 2 is a side view of the double block for boats, opposite to that shown in FIG. 1;

FIG. 3 is a view from below of the double block for boats;

FIG. 4 is a view from above of the double block for boats;

FIG. 5 is a front view of the double block for boats. 

The ornamental design for a double block for boats, as shown. 